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Short-term fish tox

According to an expert review, the acute toxicity to the Channel catfish (Ictalurus punctatus), Bluegill (Lepomis macrochirus) and Fathead minnow (Pimephales promelas) of Chlorowax 500C (a C12 chlorinated paraffin; 59% chlorinated) was determined in a static test system at 20oC, and also to rainbow trout (Oncorhynchus mykiss) at 10oC. The 96 h LC50 values were greater than 300 mg/L for the catfish, Bluegill and trout, and greater than 100 mg/L for the minnow (Howard et al. 1975).

A fish acute toxicity test was performed to determine the 96 h LC50 in the bleak (Alburnus alburnus) of five SCCPs; the C10-13 chlorinated paraffins Witaclor 49 (49% Cl), Witaclor 55EN (56% Cl), Witaclor 63 (63% Cl) and Witaclor 71P (71% Cl) and the C11.5 substance Chloroparaffin huls 70C (70% Cl), under static conditions. The test substances were dissolved in acetone to prepare the neccessary dilutions due to their low water solubility. At least six concentrations of each test substance was used in the study with an acetone concentration of 500 µl/L; solvent and untreated control groups were also included. No mortality was observed in bleaks exposed for 96 h in brackish water containing up to 5000 mg/L of Witaclor 49, Witaclor 63 or Witaclor 71P or up to 10,000 mg/L of Witaclor 55EN or Chloroparaffin huls 70C. Therefore, the 96 h LC50 values can be considered as greater than these concentrations (Linden et al. 1979).

In addition, Hoechst (1996; 1977) has reported 48 h LC50s of >500 mg/L for C10-12 chlorinated paraffins (of 52, 56, 58, 62 and 70% chlorination) in a static test system with the Golden orfe (Leuciscus idus).

Overall, SCCPs (of varying chlorination) appear to be of low acute toxicity to fish based on 48 and 96 h LC50s in excess of 100 mg/L in static test systems.

Long-term fish tox

In a good-quality GLP study, the 60-day LC50 value for a C10-12 chlorinated paraffin (58% chlorinated) was determined using freshwater rainbow trout (Oncorhynchus mykiss; reported as Salmo gairdneri). Groups of 30 young fish were exposed to five concentrations of test material (0.032, 0.1, 0.32, 1 and 3.2 mg/L nominal) in a flow through system and behaviour and mortality monitored throughout the study. The test material consisted of a C10-12 chlorinated paraffin (58% chlorinated) mixed with [6 -14C] chlorinated n-undecane (59.1% chlorinated) to facilitate the determination of the actual concentrations in the medium. In the first series of experiments, no mortality or abnormal behaviour was noted in the control groups (freshwater and acetone solvent control), whereas a dose-related increase in mortality (4/30, 17/29 and 24/30 at a nominal concentration of 0.1, 0.32 and 1.0 mg/L respectively) was seen in the treated groups. In additional studies (series 2 and 3), mortalities were seen in all control groups (1/30 controls in series 1 and 2 and 2/29 and 3/29 solvent controls in series 2 and 3 respectively). Abnormal behaviour, inluding lethagy, failure to feed and bouts of directionless activity were seen in all treated groups, the extent being greater at the highest exposure concentrations. A 60-day LC50 value of 0.34 mg/L was determined for this material (Madeley and Maddock, 1983a).

According to an expert review, Rainbow trout (Onchorynchus mykiss) were exposed to a C10-12 chlorinated paraffin (58% chlorinated) in a flow-through system at 10oC for up to 20 days. Although not clear from the report, it appears concentrations of between 0.04 and 100 mg/L were used. A LC50 of more than 100 mg/L after 24 days was noted. Various sub-lethal effects were reported resulting in a progressive loss of motor function and immobilisation, beginning within 15 to 20 days of the start of exposure. When death occured it resulted from debilitation, cessation of feeding and other secondary effects. The NOEC for the C10-12 chlorinated paraffin was less than 0.04 mg/L in this study (Howard et al. 1975).

In a good-quality GLP study, the toxicity of Chlorowax 500C (a C10 -12 chlorinated paraffin; 58% chlorination) to Cyprinodon variegatus (sheepshead minnow) was determined in a 32-day flow-through toxicity test. Embryos and larvae were exposed to nominal concentrations of 0, 56, 100, 320, 560 or 1000 ug/L in saltwater and observations of the percentage hatch of embryos, percentage survival of hatched embryos and total lengths and weights of the larvae at the end of the study were made. No significant effects on hatchability of embryos or on survival of the larvae were noted at any of the test concentrations when compared with saline or vehicle control populations. However, length and weight of the larvae were found to be significantly smaller (p=0.05) at the highest tested concentration of 1000 ug/L (mean measured concentration 620.5 ug/L) when compared with the vehicle control larvae, while length and weight at nominal concentrations of 56 and 100 ug/L were significantly increased. A decrease in length or weight of larvae is considered to be an exposure related detrimental effect. Therefore, the NOEC in this study was found to be a nominal concentration of 560 ug/L, corresponding to a mean measured concentration of 280 ug/L (Hill and Maddock, 1983a).

During fourteen day exposures to 125 μg/L of various C10 -13 chlorinated paraffins (49, 59 and 71% chlorination) behavioural effects including sluggish movements, lack of shoaling and abnormal posture were noted in the bleak (Alburnus alburnus). These effects were reversible after two days in clean brackish water (Bengtsson et al. 1979).

Short-term aquatic inverts

A number of studies have been conducted to assess the short-term toxicity of SCCPs to Daphnia magna and other aquatic invertebrates.

In a well reported, good quality study to GLP, the acute toxicity of Chlorowax 500C (a C10-12 chlorinated paraffin; 58% chlorination) to the freshwater crustacean, Daphnia magna, was determined in a static system. Groups of 20 Daphnia, aged <24 h, were exposed to nominal concentrations of 0, 18, 32, 56, 100, 180, 320 or 560 µg/L for up to 48 h. The Daphnia were not fed during the course of the test and immobilisation was assessed after 24 and 48 h. The 48 h EC50 for immobilisation to Daphnia magna was estimated, based on measured concentrations, to be 530 µg/L (95% CL 355-1540 µg/L). This value was in excess of the maximum measured concentration tested of 415 µg/L, since the test substance caused the Daphnia to float, on or near the surface of the solution, at measured concentrations of approximately 75 µg/L and above (Thompson and Madeley, 1983a). According to the final RAR (EU, 2000), 24 h EC50s for D. magna reportedly ranged from 0.3 mg/L for a C10 -13 chlorinated paraffin (61% chlorination) to 11.1 mg/L for a C10 -13 chlorinated paraffin (56% chlorination), at 21oC using acetone as a cosolvent (Huels, 1984). There appears to be no clear pattern with regard to the effects of the carrier substance or the degree of chlorination on the acute toxicity of SCCPs to D. magna.

In a well reported, good quality GLP study, the acute toxicity to the marine mysid shrimp, Mysidopsis bahia, of Chlorowax 500C (a C10-12 chlorinated paraffin; 58% chlorination) was determined in a saltwater flow-through system. Duplicate vessels each containing 20 shrimps/test group, aged <24 h (Series 1) or aged <72 h (Series 2), were exposed to nominal concentrations of Chlorowax 500C of 0, 18, 32, 56 and 100 µg/L (Series 1) or 0, 5.6, 10, 18 and 32 µg/L (Series 2) for up to 96 h. The animals were fed throughout the exposure period and mortality was assessed after 24, 48, 72 and 96 h. The 24, 48, 72 and 96 h LC50s for the <24 h old mysid shrimp (Series 1), based on measured concentrations, were calculated to be >84.4, 22.3, 16.7 and 15.5 µg/L, respectively. The 72 and 96 h LC50s for the <72 h old shrimp (Series 2) were 20.0 and 14.1 µg/L, respectively. The lowest measured concentration causing significant mortality (50%) at 96 h was 13.7 µg/L (Thompson and Madeley, 1983d).

No adverse effects were reported during the second instar of the midge Chironomus tentans following exposure to a C10-12, 58% chlorinated paraffin (in acetone) at levels up to 162 μg/L for 48 hours, considered the NOEC in this study (E & G Bionomics, 1983).

Long-term aquatic inverts

In a well conducted GLP study, the 21-day toxicity of Chlorowax 500C (a C10-12 chlorinated paraffin; 58% chlorination) to D. magna was investigated using a continuous flow procedure (in brackish water). Replicate samples of 10 Daphnia/group, aged <24 h, were exposed to nominal concentrations of 3.2, 5.6, 10, 18, 32 and 56 ug/L (mean measured concentrations of 2.7, 5.0, 8.9, 16.3, 25.5 and 38.7 ug/L) for 21 days. The animals were fed throughout exposure and the effects on survival, reproduction and growth were assessed. All parent Daphnia exposed to measured concentrations of 16.3 ug/L and above died within 6 days. Only one animal was recorded as immobilised in addition to the mortalities and therefore immobilisation effects were not analysed separately. In the surviving groups, there was no significant effects on parental length or on total young production. Offspring were produced in all vessels by day 8, with a significantly greater number of those produced at a measured concentration of 8.9 ug/L being found dead when compared with the solvent controls. There were no significant effects on survival, reproduction and growth (length after 21 days) for Daphnia exposed to a measured concentration of up to 5 ug/L.Therefore, the NOEC for Chlorowax 500C under these conditions was 5 ug/L and the LOEC was 8.9 ug/L. The "maximum acceptable toxicant concentration" (MATC) was, therefore, between 5.0 and 8.9 ug/L, the geometric mean being 6.7 ug/L (Thompson and Madeley, 1983a). According to the final RAR (EU, 2000), 21 d EC50s for D. magna reportedly ranged from 0.101 mg/L for a C10-13 chlorinated paraffin (60% chlorination) to 0.228 mg/L for a C10 -13 chlorinated paraffin (20% chlorination), with emulsifier (Huels, 1984, 1986).

In a well reported, good quality GLP study, the chronic toxicity of Chlorowax 500C (a C10-12 chlorinated paraffin; 58% chlorination) to the marine mysid shrimp, Mysidopsis bahia, was investigated in a flow-through system. Replicate samples of 20 shrimp/group, aged <48 h, were exposed to nominal concentrations of 0, 1.0, 1.8, 3.2, 5.6 and 10 µg/L (mean measured concentrations of 0, 0.6, 1.2, 2.4, 3.8 and 7.3 µg/L) for 28 d. The animals were fed throughout the exposure period and the effects on survival, sexual maturation, reproduction and final size assessed. There were no significant effects of treatment on sexual maturation, reproduction or final body length. However, the percentage mortality at the measured concentrations of 1.2 and 2.4 µg/L was significantly increased (P=0.05) when compared with the controls. No significant difference was seen when compared with the solvent controls and since the mortalities at the higher dose levels were not significantly different from either of the control groups, it was concluded that the mortalities were not related to treatment with the test substance. The 28-d NOEC for Chlorowax 500C to the marine mysid shrimp was, therefore, determined to be 7.3 µg/L, the highest mean measured concentration tested, under the conditions of this study (Thompson and Madeley, 1983d).

The midge Chironomus tentans was exposed to a C10-12, 58% chlorinated paraffin (in acetone) at concentrations of 61 to 394 μg/L in water over the whole of its 49 day life cycle. No significant response, except in halting adult emergence at 121 and 394 μg/L, was reported, leading to a MATC of between 78 and 121 μg/L, with a geometric mean of 97 μg/L, and a NOEC of 61 μg/L (E & G Bionomics, 1983).

In a GLP study, the 60-day toxicity of Chlorowax 500C (a C10 -12 chlorinated parrafin; 58% chlorination) to the mussel (Mytilus edulis) was determined in a flow-through system. Mussels were exposed to seawater containing nominal concentrations of 0, 0.018, 0.056, 0.1, 0.32 and 3.2 mg/L (resulting in mean measured concentrations of 0, 0.013, 0.044, 0.071, 0.13 and 0.93 mg/L, respectively) and mortality was assessed after 60 days. The 60-day LC50 was estimated, based on the mean measured exposure concentrations, to be 0.074 mg/L. Significant mortality occurred on exposure to measured concentrations of 0.071, 0.13 and 0.93 mg/L, and for each, the median lethal time (LT50; defined as the time calculated from the data obtained, required to result in 50% mortality at the exposure concentration specified) was calculated to be 59.3, 39.7 and 26.7 days, respectively. No significant mortality was observed at measured concentrations of 0.013 and 0.044 mg/L (considered the NOEC in this study) (Madeley and Thompson, 1983).

A further study on Mytilus edulis using a C10 -12, 58% chlorinated paraffin was carried out by Thompson and Shillabeer (1993). Groups of 30 mussels were exposed to measured concentrations of 2.3 or 9.3 μg/L in seawater for 12 weeks in a flow-through system. No mortalities were seen in any of the exposure groups or controls, but growth (as assessed by increase in shell length and tissue weight) was significantly reduced in the group exposed to 9.3 μgL. No significant effects were seen in the group exposed to 2.3 μg/L.

The NOEC of 0.005 mg/L (Thompson and Madeley, 1983a) for the C10-12, 58% chlorinated paraffin shows that D. magna is the most sensitive aquatic species tested, and this value will be taken forward to the risk characterisation for the aquatic compartment.

Tox to aquatic algae

In a well reported study, the toxicity of Chlorowax 500C (a C10 -12 chlorinated paraffin; 58% chlorination) to the marine alga, Skeletonema costatum, was investigated. Triplicate samples of the 5-day old culture were exposed to nominal concentrations of 0, 5.6, 10, 18, 32, 56 or 100 ug/L (mean measured concentrations of 0, 4.5, 6.7, 12.1, 19.6, 43.1 or 69.8 ug/L) for up to 10 days. Six replicate control and three replicate solvent control cultures were also used. The effects on cell density were assessed by measuring the absorbance and particle count, and the effects on growth rate were also examined. The test substance affected growth during the early stages of the test but the affected cultures ultimately attained cell densities similar to the controls. After 4 days, cell density, as estimated by absorbance, was significantly lower (p=0.01) than in the solvent control at nominal concentrations of 56 ug/L and 100 ug/L (the highest tested concentration), at which the reductions compared with the solvent control were 18 and 74%, respectively. After 10 days, there were no significant differences between the test substance treatments and the solvent control. Growth rates during the first 2 days were significantly lower (p=0.01) than in the solvent control at nominal concentrations of 32 ug/L and above, but remained lower only for the 100 ug/L treatment during the day 2-3 interval. Growth rates after day 3 were at least as great as in the solvent control for all treatments. The 96h EC50s for cell density, based on measured concentrations, were 0.056 and 0.043 mg/L when measured by absorbance and particle count, respectively. The 48 h EC50 for growth rate was 0.032 mg/L and a 96 h NOEC of 0.012 mg/L was obtained (Thonpson and Madeley, 1983c).

In a well reported study, the toxicity of Chlorowax 500C (a C10 -12 chlorinated paraffin; 58% chlorination) to the freshwater alga, Selenastrum capricornutum, was investigated. Algae were exposed to nominal concentrations of 0, 0.18, 0.32, 0.56, 1.0, 1.8 and 3.2 mg/L (mean measured concentrations of 0, 0.11, 0.22, 0.39, 0.57, 0.90 and 1.2 mg/L) for up to 10 days and the growth of the algae was assessed by the measurement of cell densities by particle count at intervals during the study. The lowest measured concentration tested resulting in a significant inhibition of growth was 0.57 mg/L and the NOEC was therefore 0.39 mg/L. The 4, 7 and 10 day EC50s for cell density, based on the measured concentrations, were calculated by probit analysis to be 3.7, 1.6 and 1.3 mg/L respectively. It was noted that these EC50 values are extrapolated values, as they exceeded the highest mean measured concentration of the test substance (1.2 mg/L) employed in the study, this being considered the maximum that could be tested due to the low solubility of the test substance (Thompson and Madeley, 1983b).

Toxicity to microorganisms

Toxicity data available for the effects of C10-13 chlorinated paraffins (52-70% chlorination) on bacteria, suggest that SCCPs are of low toxicity to microorganisms.

In a well conducted GLP study, the toxicity of Chlorowax 500C (a C10-12 chlorinated paraffin; 58% chlorination) to the anaerobic sewage sludge digestion process was investigated. Toxic effects, after treatment of a mixture of feed and digested sludges with concentrations of 0.56, 1.0, 1.8, 3.2, 5.6 and 10% chlorinated paraffin w/w with respect to digester volatile suspended solids content, were assessed by the measurement of the degree of inhibition of gas production at various time intervals of up to 10 days. Significant inhibition of gas production occurred at concentrations of 3.2, 5.6 and 10% w/w (which equates to 32,000 mg/L and above) during the first 3-4 days of treatment. Recovery was seen after this time, which continued up to day 10. No significant effects were noted at 18,000 mg/L and below. This study showed that short term exposure to Chlorowax 500C concentrations of 32,000 mg/L and above may cause transient partial inhibition of gas production. However, recovery of affected digesters is likely to be rapid with no long-term effects (Madeley et al. 1983b).

According to the final RAR (EU, 2000), SCCPs were of low acute toxicity to anaerobic bacteria from a domestic wastewater treatment plant, with toxicity seen at 5000, 1700, 2500, 2000 mg/L for 52, 56, 58 and 62%, C10 -13 chlorinated paraffins, respectively (Hoechst AG, 1977) and the lowest toxic concentration of 600 mg/L reported for a 70%, C10 -13 chlorinated paraffin (Hoechst AG, 1976). The LOEC of 600 mg/L will be taken forward to the risk characterisation.

References (for which no ESR has been created - please move to reference list in CSR)

Bengtsson B. E. and Baumann Ofstad E. (1982). Long-term studies on uptake and elimination of some chlorinated paraffins in the bleak Alburnus alburnus. Ambio, 11, 38-40.

E & G Bionomics (1983). Acute and chronic toxicity of a chlorinated paraffin to the midge Chironomus tentans. United States Environmental Protection Agency Document # 88-8300549 (cited in EU, 2000).

Hoechst AG (1976). Unveroeffentlichte Untersuchung (19.05.1976) (cited in EU, 2000).

Hoechst AG (1977). Unveroeffentlichte Untersuchung (28.11.1977) (cited in EU, 2000).

Huels (1984). Unveroeffentlichte Untersuchung Daphnien (cited in EU, 2000).

Huels (1986). Unveroeffentlichte Untersuchung Daphnien (cited in EU, 2000).

Thompson R. S. and Shillabeer N. (1983). Effect of a chlorinated paraffin on the growth of mussels (Mytilus edulis). ICI Confidential report BL/B/2331 (cited in EU, 2000).